As semiconductor devices have been becoming finer in recent years, various material films having different properties are formed on a substrate, and are processed. In particular, in a damascene interconnect forming process in which interconnect trenches formed in a dielectric film are filled with a metal, an excessive metal is polished away by a polishing apparatus after a metal film is formed. Various films, such as a metal film, a barrier film, and a dielectric film, are exposed on a wafer surface that has been polished. Residues, such as slurry used in polishing and polishing debris, remain on these films that are exposed on the wafer surface. In order to remove these residues, the polished wafer is transported to a substrate cleaning apparatus, where the wafer surface is cleaned.
If the cleaning of the wafer surface is insufficient, reliability problems, such as poor adhesion and a current leak due to the existence of the residues, may occur. Therefore, in manufacturing of a semiconductor device, cleaning of the wafer has been an important process for improving a yield of products.
A substrate cleaning apparatus of pen-type is known as the aforementioned substrate cleaning apparatus. The substrate cleaning apparatus of this pen-type is configured to clean a wafer by bringing a pen-sponge into sliding contact with a surface of the wafer while supplying cleaning liquid (e.g., chemical liquid or pure water) onto the surface of the wafer. More specifically, the pen-sponge is moved on the wafer surface while being rotated about an axis of the pen-sponge. The surface of the wafer is cleaned by the pen-sponge in the presence of the cleaning liquid.
As the cleaning of the wafer with use of the pen-sponge is repeated, particles, such as abrasive grains contained in a polishing liquid and/or polishing debris, are accumulated in the pen-sponge. Therefore, as shown in FIG. 16, in order to clean a pen-sponge 200, a cleaning element 201 is provided adjacent to the wafer. This cleaning element 201 has a flat cleaning surface 201a. The pen-sponge 200 is pressed against the cleaning surface 201a of the cleaning element 201 while the pen-sponge 200 is being rotated about its own axis. Further, pure water is supplied onto the cleaning surface 201a of the cleaning element 201. In this state, the pen-sponge 200 is cleaned by sliding contact with the cleaning element 201.
However, since the pen-sponge 200 is pressed against the flat cleaning surface 201a of the cleaning element 201, a central area of the pen-sponge 200 may not be cleaned sufficiently. In addition, the particles that have been once removed from the pen-sponge 200 and moved to the cleaning element 201 may be attached again to the pen-sponge 200.